Liquid Composite Molding (LCM) is a category of composite manufacturing processes which can create strong lightweight composite materials from various types of fibers and thermosetting resins. Such closed mold processes are becoming more viable because of increasing regulations involved with the use of resin systems containing Volatile Organic Compounds (VOCs) such as styrene. Using closed mold processes reduces the amount of VOCs released into the atmosphere during the manufacturing process. Exemplary LCM processes include the Resin Transfer Molding (RTM) process. RTM technology is best characterized by the use of a rigid two sided matched mold in which the dry preforms are placed. Resin is then injected at constant pressure or constant flow rate until it reaches a desired vent. The resin is then allowed to cure before demolding the part. The tooling cost for this process increases exponentially with the increase in the size of the part to be manufactured.
One exemplary LCM process is known as Vacuum Assisted Resin Transfer Molding (VARTM). The VARTM process reduces tooling costs by using only a single, lightly-constructed mold in which the second molding surface is replaced with a polymer film adhered to the molding surface with a sealant tape. A vacuum pump is used to evacuate the air from the mold and compact the preform fabric. Once the mold is leak-checked, a tube connected to a resin bucket is opened to draw the resin into the mold which flows through the preform toward the vent. Once the resin reaches the vent, the injection is discontinued but the vacuum is maintained until the resin cures. Although the VARTM process may reduce capital investment, it is labor intensive and is more prone to variability in part quality due to human error, which has limited its use. A second limitation with VARTM processes arises from inherent permeability variations within the preform, which often leads to resin filling patterns that leave dry, unfilled regions within the mold. To address this deficiency, recent research into the process has provided an improved understanding and subsequently a greater potential to enhance the consistency of the manufactured parts. Accordingly, there is a need in the art for computer controlled automation to increase the reliability and repeatability of VARTM processes.